1. Field of the Invention
This invention relates to an outboard motor steering control system.
2. Description of the Related Art
Conventionally, a hydraulic steering mechanism that is equipped with a hydraulic cylinder, utilizes a helm pump to discharge or delivery hydraulic oil by the amount in response to turning of a steering wheel and supplies the discharged oil via tubes to the hydraulic cylinder, thereby enabling to steer the outboard motor with respect to the hull (boat), is well-known as a type of steering systems of outboard motors, for example, as taught by Japanese Laid-Open Patent Application No. Sho 62(1987)-125996 (particularly in FIG. 2 etc.). In such a hydraulic steering mechanism, since an outboard motor and a steering wheel are mechanically connected, the operator can feel external force acting on the outboard motor from load of the steering wheel and can experience direct steering feel. This is also the same in a manual steering mechanism which steers an outboard motor through a push-pull cable in response to the operator's turning of a steering wheel.
Aside from the above, an electric steering mechanism is recently proposed which is equipped with an electric motor that is connected to a steering shaft of the outboard motor, detects turned amount of a steering wheel and controls the operation of the electric motor based on the detected rotation angle to steer the outboard motor with respect to the hull, for example, as taught by Japanese Laid-Open Patent Application No. 2002-187597 (particularly paragraphs 0011, 0025 and 0027 and FIG. 1). Since this type of the electric steering mechanism has no mechanical connection between the outboard motor and the steering wheel, even when the steering load of the outboard motor is heavy, the burden on the operator can advantageously be lightened, thereby enabling to achieve the facilitated operating feel.
However, since an outboard motor is normally provided with either the hydraulic steering mechanism or the electric steering mechanism, when the operator is not satisfied with the steering or operating feel, he/she must replace the mechanism to another or change the outboard motor as a whole, rendering difficult to cope with the operator's preference of steering feel. Further, in the case of occurrence of a steering mechanism failure, it is difficult to continue the steering operation of the outboard motor.